A similar device is known from DE-PS 2635 635. The electrical discharge occurs in between the electrodes, which are placed in liquid and in the first focus of an ellipsoid. After the electrical discharge, because of the explosive evaporation of the liquid, a shock wave is propagated and is focused into the second focus of the ellipsoid. The calculi to be disintegrated are placed in this second focus. In addition to the shock wave, low frequency parts are emitted by the cavitation bubble. The low frequency sound waves which are placed in the audible region are disturbing for a patient as well as for personnel, because of their high amplitude. Additionally, these low frequency waves induce pain during therapy.
The usage of an electrolyte as a liquid medium which surrounds the electrodes is also known.